North Korea, angry at new sanctions imposed on it for testing nuclear weapons, has made increasingly strident warnings of an imminent war with South Korea and the United States.
It told diplomats on Friday to consider leaving Pyongyang because of rising tension, but diplomatic missions appeared to view the appeal as more rhetoric and stayed put.
The United States, keen to avoid actions which could provoke the North, on Saturday postponed a long-scheduled missile test in California.
China is North Korea's sole major diplomatic and financial backer, but official statements have reflected a degree of impatience at the actions of authorities under 30-year-old leader Kim Jong-un.
"At present tensions on the Korean peninsula are rising unceasingly, and China expresses grave concern about this," China's Foreign Ministry said in a statement on its website.
"The Chinese government has already asked the North Korea side to earnestly ensure the safety of Chinese diplomats in North Korea, in accordance with the Vienna Convention and international laws and norms."
The Chinese embassy, it said, was "understood" to be operating normally in Pyongyang. China would "protect the legal rights and safety of Chinese citizens and Chinese-invested organisations in North Korea".
A ministry statement late on Saturday quoting Foreign Minister Wang Yi, said Beijing would "not allow troublemaking on China's doorstep".
Chinese President Xi Jinping, addressing a forum on Sunday, appeared to refer further to boosted tensions when he said no country "should be allowed to throw a region and even the whole world into chaos for selfish gain".
"Stability in Asia now faces new challenges, as hot spot issues keep emerging and both traditional and non-traditional security threats exist," he said on the southern island of Hainan.
In Washington, a defence official said a test of the Minuteman III intercontinental missile, scheduled for next week at the Vandenberg Air Force Base in California, would now be postponed.
"This is the logical, prudent and responsible course of action to take," the official said, speaking on condition of anonymity.
He said the test had been unconnected to "anything related to North Korea" and added that another test launch could be expected next month. The United States remained fully prepared to respond to any North Korean threat, the official said.
North Korean anger over the sanctions following its third nuclear weapons test in February has been compounded by joint US-South Korean military exercises that began on March 1.
North Korea has always condemned the exercises held by US forces and their South Korean allies. But its comments have been especially vitriolic this year as the United States dispatched B-2 bombers from its home bases to stage mock runs.
China's Xinhua news agency, reporting on the North's suggestion to diplomats to evacuate, quoted the North's Foreign Ministry at the weekend as saying the issue was no longer whether but when a war would break out.
North Korean television provided little evidence of tension in the reclusive state on Sunday, with newscasts showing old footage of Kim visiting military units and other items concerning the country's leaders.
Nor was there any trace of tension in the South Korean capital, Seoul, with residents ignoring an early spring chill to stroll in the city centre.
South Korean media on Friday said the North had moved two medium-range missiles to the country's east coast, but there has been no confirmation of such a move. That prompted the White House to say that Washington would "not be surprised" if the North staged another missile test.
Kim Jong-un is the third member of his dynasty to rule North Korea. He took over in December 2011 after the death of his father, Kim Jong-il, who staged confrontations with South Korea and the United States throughout his 17-year rule.
Russia's ITAR-TASS news agency, in a dispatch from London, quoted British diplomatic sources as saying North Korea believed the situation could be stabilised if US President Barack Obama personally called Kim.
"North Korea is waiting for that call from Washington," Tass quoted the source as saying.
North Korea has not shut down a symbol of joint cooperation with the South, the Kaesong industrial zone just inside its border. But last week it prevented South Koreans from entering the complex and about 100 of them who remained were due to return home on Saturday, leaving a further 500 there.
On Sunday, a South Korean who had fallen ill was taken out of the industrial zone by car. – Reuters